In one method of manufacturing electrical terminals, the terminals are stamped and formed from metal strip and are attached to a carrier strip. This carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One necessary manufacturing operation involves plating, i.e., electroplating the electrical contact surfaces of the strip fed terminals with a contact metal, usually noble metals or noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating will enhance conductivity of the terminals. The high cost of these metals has necessitated precision deposition on the contact surfaces of the terminals, and not on surfaces of the terminals on which plating is unnecessary.
Apparatus for plating is called a plating cell and includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., and electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the terminals, which comprise the cathode of the plating cell. The metal ions deposit as metal plating on those terminal surfaces in contact with the plating solution.
There are disclosed in U.S. Pat. Nos. 4,384,926, 4,427,498 and 4,555,321, owned by this assignee, plating apparatuses in which the interior surfaces of strip fed terminals can be plated by supplying plating fluid through nozzles and over associated anode extensions or assemblies that are mounted for reciprocation into and out of the interiors of terminals. In effect, each anode extension, nozzle and terminal is a plating cell, the apparatus comprising a plurality of plating cells. In the first two patents, the anode extensions are mounted within their associated nozzles. In the third patent, the anode extensions are mounted separately and apart from the nozzles and enter the terminals from a different direction than that of the plating fluid.
The apparatuses disclosed in the three referenced patents are designed to be used with stamped and formed terminals, wherein the contact zone is located on an inside surface of a formed terminal. To selectively plate the contact zone the anode extension must be moved inside the terminal. To obtain an even distribution of plating in the contact zone, it is preferable that the anode member of the anode extension be concentrically aligned within the contact zone of the terminal. If the anode is not aligned concentrically in the terminal, an uneven layer of plating material is deposited. Furthermore for plating to occur, it is essential that the conductive anode member not come into physical contact with the terminal, which is the cathode. Should the anode touch the terminal, a short circuit results and no plating will occur in that cell.
To ensure accurately reproducable and uniformly deposited plating it is also necessary to precisely control the tolerances of the various components of the plating apparatus, and in particular the anode extension members. It is also important to control the tolerances in the stamped and formed terminal strips. Variations in alignment of the terminals on the strip, such as a terminal that is even slightly askew can cause the anode member to become bent and misaligned with that terminal and succeeding terminals presented to the bent anode. Furthermore, if the anode member is significantly damaged, the apparatus may jam, the strip of stock may break or the stock may have to be scrapped because of damaged terminals.
In addition to aligning the anode member within the terminal, it is also important that there be an essentially uniform current present in each of the plating cells of the plating apparatus. In each apparatus of the previous patents, electrical connection depends upon physical contact between a part of a conductive anode extension and an electrically charged member within the apparatus. This physical contact is aided by the use of spring members either in the anode extensions or the apparatus itself. Failure to achieve electrical interconnection of an anode extension causes a fluctuation in the amount of current in the remaining operating cells.
In order to minimize the aforementioned problems it is desirable to provide a means for ensuring a concentric alignment of anode members in the terminals to be plated. It is also desirable to provide means for ensuring that an essentially uniform current be "present" in each of the cells of the apparatus.